Lithium ion batteries and methods of sterilization

ABSTRACT

A lithium ion battery is provided that includes: a positive electrode; a negative electrode; a separator comprising a material having a melt temperature of greater than 150° C.; and an electrolyte including an organic solvent and a lithium salt. A method for sterilizing a lithium ion battery is also provided that includes: providing a lithium ion battery (particularly one as described herein); either charging or discharging the battery to a state of charge (SOC) of 20% to 100%; and steam sterilizing the battery to form a sterilized lithium ion battery.

This application claims the benefit of provisional patent applicationNo. 62/435,237 entitled “Lithium Ion Batteries and Methods ofSterilization” filed Dec. 16, 2016.

BACKGROUND

For many surgical powered tools the ability to be both cordless andrechargeable has been a major selling feature. For such high powered,high energy applications, the use of lithium ion battery technology isparticularly well suited. In order to be used in an operating room,however, the surgical instrument must be sterilized.

There are three approaches currently used to address this problem:

(1) Aseptic transfer of the battery into a sterile device. This requirestwo people to set up the device, one to handle the unsterile battery andthe other to remain in the sterile field and only handle the sterile(e.g., autoclaved) device once the battery was inserted by the otherperson.

(2) STERRAD, which includes hydrogen peroxide vapor and low-temperaturegas plasma low temperature sterilization of the battery pack(temperature less than 55° C.). This requires specialized additionalequipment to be purchased by the hospitals.

(3) Aseptic transfer into sterile clamshell. This requires additionalpackaging and two people for aseptic transfer as described in approach(1). In order to improve case-of-use and minimization of additionalhospital equipment, it would be beneficial to be able to autoclave theentire instrument. In order to achieve this goal, the lithium ionbattery must withstand a standard steam autoclave cycle (134° C. for 18minutes) and maintain usability at application temperature for 100 to300 cycles.

Many components of current commercial lithium ion batteries cannotwithstand the extreme temperatures of approach (3). For example,polyethylene, a component of a commonly used tri-layer shutdownseparator, melts at or below 130° C. Linear carbonate solvents used incommercial lithium ion batteries can have a low boiling point (less than140° C.). Also, LiPF₆, a commonly used electrolyte salt decomposes near80° C. Furthermore, corrosion of the metal current collectors is greatlyaccelerated at high temperatures, which can lead to delamination of theactive material. Thus, lithium ion batteries are needed that withstandthe conditions of steam autoclave conditions.

SUMMARY

The present disclosure is directed to lithium ion batteries, as well asmethods of sterilizing such batteries.

Such lithium ion batteries have a lithium ion cell chemistry with uniquecombinations of current collectors, electrolytes, separators, and cellencasements, which can withstand the conditions experienced in anautoclave, and suffer very little to no detectable loss in applicationtemperature performance compared to an otherwise identical cell notsubjected to the autoclave conditions.

In one embodiment, a lithium ion battery is provided that includes: apositive electrode; a negative electrode; a separator that includes amaterial having a melt temperature of greater than 150° C.; and anelectrolyte including an organic solvent and a lithium salt; wherein theorganic solvent includes a solvent having a boiling point below 140° C.(e.g., a linear carbonate); and wherein the lithium salt includeslithium bis(trifluoromethanesulfonimide) (LiTFSI). The positiveelectrode includes: a positive current collector including aluminum;positive electrode material including a lithium-containing metal oxideor a lithium-containing metal phosphate; a binder; and conductivecarbon. The negative electrode includes: a negative current collectorincluding copper, aluminum, titanium, or carbon; negative electrodematerial including a lithium titanium oxide, a carbon-containingmaterial capable of intercalating lithium, a metal-alloy containingmaterial capable of intercalating lithium, or a combination thereof; abinder; and conductive carbon. For such battery, after exposure toconditions that include a temperature of at least 100° C. for a time ofat least 4 minutes, the battery retains a capacity of at least 80% ofthe capacity at application temperature of a battery having the sameconstruction that has not been subjected to such conditions.

In another embodiment, a lithium ion battery is provided that includes:a positive electrode; a negative electrode; a separator having a melttemperature of greater than 150° C.; an electrolyte; and a hermeticallysealed encasement. The electrolyte includes: a lithium salt including acombination of LiTFSI, LiBOB, and LiPF₆, wherein the LiPF₆ is present inan amount of no greater than 25 mol-% of the total moles of electrolytesalt (or at a concentration of up to 0.3M); and an organic solventincluding a mixture of ethylene carbonate (EC) and ethylmethyl carbonate(EMC). The positive electrode includes: a positive current collectorincluding carbon-coated aluminum; positive electrode material includingLiCoO₂; a binder; and conductive carbon. The negative electrodeincludes: a negative current collector including copper; negativeelectrode material including artificial graphite; a binder; andconductive carbon. For such battery, after exposure to conditions thatinclude a temperature of at least 100° C. for a time of at least 4minutes, the battery retains a capacity of at least 80% of the capacityat application temperature of a battery having the same constructionthat has not been subjected to such conditions.

In yet another embodiment, a method for sterilizing a lithium ionbattery, the method includes: providing a lithium ion battery (e.g.,particularly one as described herein), either charging or dischargingthe battery to a state of charge (SOC) of 20% to 100%, or of 20% to 80%;and steam sterilizing the battery to form a sterilized lithium ionbattery.

The term “application temperature” means a temperature within a range of10° C. to 45° C.

The terms “comprises” and variations thereof do not have a limitingmeaning where these terms appear in the description and claims. Suchterms will be understood to imply the inclusion of a stated step orelement or group of steps or elements but not the exclusion of any otherstep or element or group of steps or elements. By “consisting of” ismeant including, and limited to, whatever follows the phrase “consistingof.” Thus, the phrase “consisting of” indicates that the listed elementsare required or mandatory, and that no other elements may be present. By“consisting essentially of” is meant including any elements listed afterthe phrase, and limited to other elements that do not interfere with orcontribute to the activity or action specified in the disclosure for thelisted elements. Thus, the phrase “consisting essentially of” indicatesthat the listed elements are required or mandatory, but that otherelements are optional and may or may not be present depending uponwhether or not they materially affect the activity or action of thelisted elements.

The terms “preferred” and “preferably” refer to embodiments of thedisclosure that may afford certain benefits, under certaincircumstances. However, other embodiments may also be preferred, underthe same or other circumstances. Furthermore, the recitation of one ormore preferred embodiments does not imply that other embodiments are notuseful, and is not intended to exclude other embodiments from the scopeof the disclosure.

As used herein, “a,” “an,” “the,” “at least one,” and “one or more” areused interchangeably. Thus, for example, a device that comprises “a”capacitor can be interpreted to mean that the device includes “one ormore” capacitors.

As used herein, the term “or” is generally employed in its senseincluding “and/or” unless the content clearly dictates otherwise. Theterm “and/or” means one or all of the listed elements or a combinationof any two or more of the listed elements (e.g., delivering therapyand/or monitoring physiological signals means delivering therapy,monitoring physiological conditions, or doing both monitoring anddelivering).

Also herein, all numbers are assumed to be modified by the term “about”and preferably by the term “exactly.” Notwithstanding that the numericalranges and parameters setting forth the broad scope of the disclosureare approximations, the numerical values set forth in the specificexamples are reported as precisely as possible. All numerical value,however, inherently contain certain errors necessarily resulting fromthe standard deviation found in their respective testing measurements.

Also herein, the recitations of numerical ranges by endpoints includeall numbers subsumed within that range (e.g., 1 to 5 includes 1, 1.5, 2,2.75, 3, 3.80, 4, 5, etc.).

Reference throughout this specification to “one embodiment,” “anembodiment,” “certain embodiments,” or “some embodiments,” etc., meansthat a particular feature, configuration, composition, or characteristicdescribed in connection with the embodiment is included in at least oneembodiment of the disclosure. Thus, the appearances of such phrases invarious places throughout this specification are not necessarilyreferring to the same embodiment of the disclosure. Furthermore, theparticular features, configurations, compositions, or characteristicsmay be combined in any suitable manner in one or more embodiments.

The above summary of the present disclosure is not intended to describeeach disclosed embodiment or every implementation of the presentdisclosure. The description that follows more particularly exemplifiesillustrative embodiments. In several places throughout the application,guidance is provided through lists of examples, which examples can beused in various combinations. In each instance, the recited list servesonly as a representative group and should not be interpreted as anexclusive list.

BRIEF DESCRIPTION OF FIGURES

The figures presented herein are idealized, not to scale, and areintended to be merely illustrative and non-limiting.

FIG. 1: Discharge capacity as a function of cycle number for the finalelectrochemical performance test for Examples 1 through 4.

FIG. 2: Inset (a) of FIG. 1.

FIG. 3: Inset (b) of FIG. 1.

FIG. 4: Discharge capacity as a function of cycle number for the initialelectrochemical performance test as a function of separator type forExamples 2, 2A, 2B.

FIG. 5: Discharge capacity as a function of cycle number for the finalelectrochemical performance test for Examples 2 and 5.

DETAILED DESCRIPTION OF ILLUSTRATIVE EMBODIMENTS

The present disclosure is directed to lithium ion batteries, as well asmethods of sterilizing such batteries.

A typical battery includes one or more cells that includes a negativeelectrode (anode), a positive electrode (cathode), a separator betweenthe negative and positive electrodes; and an electrolyte (typically, aliquid electrolyte, although a gel electrolyte may also be possible)contacting the negative electrode, positive electrode, and theseparator.

Such batteries can be used in a wide variety of surgical powered tools,including, for example, ultrasonic dissectors, vessel sealing devices,staplers, orthopedic saws/drills, or the modular surgical devicedisclosed in U.S. Pat. No. 9,017,353 (Smith et al.). More generally, thetypes of surgical devices include hand-held, powered medical diagnosticand surgical tools and wearable medical devices. Examples include RFpowered surgical sealing devices, nerve integrity monitoring devices,ablation devices, powered atherectomy devices, external, wearablestimulation devices, and external, wearable diagnostic devices.

Typical lithium ion batteries operate within a narrow temperature range,from −20° C. to +60° C. with a high delivered power at room temperature.This covers the majority of uses of lithium ion batteries. There aresome specialty batteries that are designed to operate at extremely hightemperatures, including up to 180° C. for deep drilling applications(see, e.g., U.S. Pat. Pub. No. US 2006/0019164 (Bonhommet et al.)). Thisparticular battery exclusively uses high boiling point (bp) solvents (bpgreater than or equal to 140° C.) such as ethylene carbonate (EC) andpropylene carbonate (PC). At application temperature, however, thesecyclic carbonate solvents have very high viscosities (and therefore lowionic conductivities), resulting in poor application temperature powerperformance (see, e.g., Kang Xu, Chemical Reviews, 104, 4303-4417(2004)).

The lithium ion batteries of the present disclosure are simultaneouslycapable of surviving exposure to an elevated temperature as high as 140°C. for up to 3 hours (temperatures and times experienced, for example,during steam sterilization), while maintaining a high delivered powerwhen subsequently used at application temperature. In this context,“surviving” is defined as delivering at least 80% of the battery'scapacity at application temperature, compared to a battery of the sameconstruction that did not experience the exposure to the elevatedtemperature. That is, in certain embodiments, after steam sterilization,the battery retains a capacity of at least 80% of the capacity of abattery having the same construction that has not been sterilized.

The batteries of the present disclosure are capable of achieving thishigh capacity retention and power capability following high temperatureexposure through the use of at least one solvent that has a low boilingpoint (bp less than or equal to exposure temperature (approximately 140°C.)) and low viscosity (high ionic conductivity), and the use of alithium salt or combination of salts to stabilize the solvent (up to theexposure temperature), while maintaining a high electrolyte conductivityfor application temperature.

Such batteries can be subjected to steam sterilization, particularlywhile in surgical tools. Desirably, in certain embodiments, the lithiumion batteries of the present disclosure can withstand a standardautoclave cycle (e.g., 134° C. for 18 minutes). In certain embodiments,the battery retains a capacity of at least 80% of the capacity of abattery having the same construction that has not been sterilized. Incertain embodiments, such capacity is maintained at applicationtemperature after several cycles of sterilization, preferably for up tohundreds (e.g., 100 to 300) of sterilization cycles.

In certain embodiments of batteries of the present disclosure, afterexposure to conditions that include a temperature of at least 100° C.for a time of at least 4 minutes, or at least 12 minutes, or at least 18minutes, or at least 90 minutes, or at least 120 minutes, or at least180 minutes, or at least 360 minutes, the battery retains a capacity ofat least 80% of the capacity at application temperature of a batteryhaving the same construction that has not been subjected to suchconditions.

In certain embodiments of batteries of the present disclosure, afterexposure to conditions that include a temperature of at least 121° C.for a time of at least 4 minutes, or at least 12 minutes, or at least 18minutes, or at least 90 minutes, or at least 120 minutes, or at least180 minutes, or at least 360 minutes, the battery retains a capacity ofat least 80% of the capacity at application temperature of a batteryhaving the same construction that has not been subjected to suchconditions.

In certain embodiments of batteries of the present disclosure, afterexposure to conditions that include a temperature of at least 132° C.for a time of at least 4 minutes, or at least 12 minutes, or at least 18minutes, or at least 90 minutes, or at least 120 minutes, or at least180 minutes, or at least 360 minutes, the battery retains a capacity ofat least 80% at application temperature of the capacity of a batteryhaving the same construction that has not been subjected to suchconditions.

In certain embodiments of batteries of the present disclosure, afterexposure to conditions that include a temperature of at least 135° C.for a time of at least 4 minutes, or at least 12 minutes, or at least 18minutes, or at least 90 minutes, or at least 120 minutes, or at least180 minutes, or at least 360 minutes, the battery retains a capacity ofat least 80% at application temperature of the capacity of a batteryhaving the same construction that has not been subjected to suchconditions.

In certain embodiments of batteries of the present disclosure, afterexposure to conditions that include a temperature of at least 140° C.for a time of at least 4 minutes, or at least 12 minutes, or at least 18minutes, or at least 90 minutes, or at least 120 minutes, or at least180 minutes, or at least 360 minutes, the battery retains a capacity ofat least 80% at application temperature of the capacity of a batteryhaving the same construction that has not been subjected to suchconditions.

Positive Electrode

In lithium ion batteries of the present disclosure, a positive electrodeincludes a positive current collector, positive electrode material, abinder, and conductive carbon.

In certain embodiments, the positive current collector includesaluminum. In certain embodiments, the positive current collectorincludes surface-treated aluminum. In certain embodiments, thesurface-treated aluminum includes carbon-coated aluminum. The carboncoating may be a carbon nanotube coating or other carbon nano-scalecoating. An example of such a carbon nano-scale coating is disclosed inU.S. Pat. No. 9,172,085 (Ranjith Divigalpitiya et al.). Because of thelarge surface area of the nano-scale material much less of the materialis needed, and it is typically more conductive, than a conventionalcarbon-coating.

In certain embodiments, the surface-treated aluminum includes a coatingdesigned to raise the cell impedance at temperatures above 135° C. Anexample of such a coating is a positive temperature coefficient (PTC)treatment. In certain embodiments, the PTC treatment may be extendedonto the tab material that connects to the positive electrode currentcollector.

In certain embodiments, the positive electrode material includes alithium-containing metal oxide or a lithium-containing metal phosphate.In certain embodiments, the positive electrode material includes alithium-containing metal oxide, such as, for example, LiCoO₂ orLiNiCoMn/AlO₂. In certain embodiments, the positive electrode materialincludes a lithium-containing metal phosphate, such as, for example,LiFePO₄.

In certain embodiments, the positive electrode material includes alithium-containing metal oxide that is surface treated. In certainembodiments, the surface-treated positive electrode material includes asurface treatment selected from a metal oxide (Al₂O₃, etc.), a metalphosphate (LaPO₄, etc.), a metal halide, carbon, or a mixture thereof.In certain embodiments, this surface-treatment includes a positivetemperature coefficient material.

In certain embodiments, the positive electrode binder includes carboxymethyl cellulose (CMC), styrene-butadiene rubber (SBR), polyvinylidenefluoride (PVDF), polytetrafluoroethylene (PTFE), or a mixture of two ormore thereof. In certain embodiments, the positive electrode binderincludes PVDF.

In certain embodiments, the positive electrode binder is used in anamount of at least 0.1 wt-%, based on the total weight of the drycathode mix (without solvent). In certain embodiments, the positiveelectrode binder is used in an amount of up to 10 wt-%, based on thetotal weight of the dry cathode mix (without solvent).

In certain embodiments, the conductive carbon is used in an amount of atleast 0.1 wt-%, based on the total weight of the dry cathode mix(without solvent). In certain embodiments, the conductive carbon is usedin an amount of up to 10 wt-%, based on the total weight of the drycathode mix (without solvent). Types of conductive carbon include, forexample, graphite, carbon black, carbon nanotubes, and graphene.

In certain embodiments, a positive temperature coefficient material isused in an amount of at least 0.1 wt-% based on the total weight of thedry cathode mix (without solvent).

Negative Electrode

In lithium ion batteries of the present disclosure, a negative electrodeincludes a negative current collector, negative electrode material, abinder, and conductive carbon.

In certain embodiments, the negative current collector includes copper,aluminum, titanium, or carbon. In certain embodiments, the negativecurrent collector is surface treated. In certain embodiments, thesurface-treated negative current collector includes surface treatmentselected from a carbon coating, a nitrogen coating, or an oxide coating,on the copper, aluminum, titanium, or carbon.

In certain embodiments, this surface-treatment includes a positivetemperature coefficient material. In certain embodiments, the PTCtreatment may be extended onto the tab material that connects to thenegative electrode current collector.

In certain embodiments, the negative current collector includes copper,particularly when the negative electrode material includes graphite. Incertain embodiments, the negative current collector includes aluminum,particularly when the negative electrode material comprises a lithiumtitanium oxide.

In certain embodiments, the negative electrode material includes alithium titanium oxide, a carbon-containing material capable ofintercalating lithium, a metal-alloy containing material capable ofintercalating lithium, or a combination thereof.

In certain embodiments, the negative electrode material includes alithium titanium oxide. In certain embodiments, the lithium titaniumoxide is selected from the group of: Li₄M_(x)Ti_(5−x)O₁₂ (wherein M ismetal selected from aluminum, magnesium, nickel, cobalt, iron,manganese, vanadium, copper, chromium, molybdenum, niobium, orcombinations thereof and x=0-1); Li_(x)Ti_(y)O₄ (wherein x=0-4, andy=0-2); Li₂TiO₃; Li₄Ti₅O₁₂; Li₄Ti_(4.75)V_(0.25)O₁₂;Li₄Ti_(4.75)Fe_(0.25)O_(11.88); Li₄Ti_(4.5)Mn_(0.5)O₁₂; and LiM′M″XO₄(wherein: M′ is a metal selected from nickel, cobalt, iron, manganese,vanadium, copper, chromium, molybdenum, niobium, or combinationsthereof; M″ is a three valent non-transition metal; and X is zirconium,titanium, or a combination of these two). In certain embodiments, thelithium titanate spinel material is used in any state of lithiation(e.g., Li_(4+x)Ti₅O₁₂, where 0≤x≤3). In certain embodiments, the lithiumtitanium oxide is of the formula Li₄Ti₅O₁₂ (sometimes referred to asLi_(1+x)[Li_(1/3)Ti_(5/3)]O₄, with 0≤x<1).

In certain embodiments, the negative electrode material includes acarbon-containing material capable of intercalating lithium. In certainembodiments, the negative electrode material includes graphite. Incertain embodiments, the graphite includes artificial graphite (e.g.,mesocarbon microbead (MCMB)).

In certain embodiments, the negative electrode material including ametal-alloy containing material capable of intercalating lithium. Incertain embodiments, the metal-alloy containing material includessilicon-containing material or tin-containing material that is capableof intercalating lithium. The alloy material may be mixed withcarbonaceous material.

In certain embodiments, the negative electrode binder includes carboxymethyl cellulose (CMC), styrene-butadiene rubber (SBR), polyvinylidenefluoride (PVDF), polytetrafluoroethylene (PTFE), or a mixture of two ormore thereof. In certain embodiments, the negative electrode binderincludes PVDF.

In certain embodiments, the negative electrode binder is used in anamount of at least 0.1 wt-%, or at least 1 wt-%, based on the totalweight of the dry anode mix (without solvent). In certain embodiments,the negative electrode binder is used in an amount of up to 10 wt-%,based on the total weight of the dry anode mix (without solvent).

In certain embodiments, the conductive carbon is used in an amount of atleast 0.1 wt-%, based on the total weight of the dry anode mix (withoutsolvent). In certain embodiments, the conductive carbon is used in anamount of up to 10 wt-%, based on the total weight of the dry anode mix(without solvent). Types of conductive carbon include, for example,graphite, carbon black, carbon nanotubes, and graphene.

In certain embodiments, a positive temperature coefficient material isused in an amount of at least 0.1 wt-% based on the total weight of thedry anode mix (without solvent).

Separator

Lithium ion batteries of the present disclosure include a separatorbetween the negative and positive electrodes. In certain embodiments,the separator includes a material that has a melt temperature of greaterthan 150° C. In certain embodiments, the separator includes one or morelayers of material having a melt temperature of greater than 150° C.Such layers may or may not be bonded together.

In certain embodiments, the separator material having a melt temperatureof greater than 150° C. includes a polyimide, polyolefin (such aspolypropylene), polyethylene terephthalate, ceramic-coated polyolefin,cellulose, or a mixture of two or more thereof. Such materials may be inthe form of microfibers or nanofibers. In certain embodiments, theseparator includes a combination of microfibers and nanofibers. Incertain embodiments, the separator includes polyethylene terephthalatemicrofibers and cellulose nanofibers.

Such separator materials are disclosed in U.S. Pat. No. 8,936,878(Morin) and available from Dreamweaver International (Greer, S.C.) underthe tradename SILVER.

In certain embodiments, multiple separator layers may be used, each ofwhich has a melting point greater than 150° C. However, one of theselayers may have a melting point lower than the other layer and may servethe purpose of a shutdown separator. For example, an inner layer of aseparator may have a melting point of approximately 130° C. and a layerthat may have a melting point of approximately 160° C. In thisembodiment, the inner layer would melt at a temperature of 130° C.,preventing ion flow in the battery but maintaining separation betweenthe anode and cathode to prevent shorting. In other embodiments, theinner layer of the separator may have a melting point of 130° C. and theouter layer may have a melting point of >200° C. An example of a usefulmaterial having a melting point of approximately 130° C. is apolyethylene. Examples of useful materials that have a melting pointof >200° C. include polyimide, polyethylene terephthalate, cellulose,aramid fibers, ceramics, and combinations thereof. In certainembodiments, the multiple separator layers with different melting pointsmay be laminated together to form a single multi-layer compositeseparator. In certain embodiments, a layer of positive temperaturecoefficient material may be used.

In certain embodiments, the separator is no more than 250 micrometers(i.e., microns) thick. In certain embodiments, the separator is at least5 microns, or at least 10 microns thick.

Electrolyte

Lithium ion batteries of the present disclosure include an electrolytecontacting the negative electrode, positive electrode, and theseparator. The electrolyte is typically a liquid, but it may also be agel. The electrolyte includes an organic solvent and a salt.Additionally, the electrolyte may include a polymer.

In certain embodiments, the salt includes a lithium salt, particularlylithium bis(trifluoromethanesulfonimide) (LiTFSI). In certainembodiments, the electrolyte salt consists of one or more lithium salts.That is, in certain embodiments, the only salts present in theelectrolyte are lithium salts. In certain embodiments, whether othernon-lithium salts are present or not, the electrolyte includes acombination of lithium salts.

In certain embodiments, the electrolyte includes an additional lithiumsalt selected from lithium bis(oxalato)borate (LiBOB), lithiumbis(pentafluoroethylsulfonyl)imide (LiBETI), lithiumbis(fluorosulfonyl)imide (LiFSI), lithium difluoro(oxalato)borate(LiDFOB), lithium tetrafluoroborate (LiBF₄), lithiumtrifluoromethanesulfonate (LiTriflate), lithium hexafluoroarsenate(LiAsF₆), lithium hexafluorophosphate (LiPF₆), or a mixture of two ormore thereof.

In certain embodiments, the electrolyte includes LiTFSI and LiPF₆. Incertain embodiments, the electrolyte includes LiTFSI and LiBOB. Incertain embodiments, the electrolyte includes LiTFSI, LiBOB, and LiPF₆.

The use of salt blends provides surprising benefits that cannot beachieved by individual salts. These results are not predictable.

Generally, the use of LiTFSI as the only salt leads to rapid capacityloss following high temperature exposure; however, a blend of LiTFSI andLiBOB leads to much improved performance. This may be due to reducedpositive electrode current collector corrosion achieved by the saltblend.

Use of LiPF₆ alone leads to rapid mechanical and electrochemicaldegradation of cells when exposed to high temperature. Generally, theuse of a blend of LiPF₆ and LiTFSI leads to rapid loss in capacity, uponhigh temperature exposure. Use of a blend of LiPF₆, LiTFSI, and LiBOB,where the LiPF₆ amount is less than 25% of the total moles of salt showsgood high temperature stability. Further, this blend also shows improvedapplication temperature power capability. The following embodimentsencompass these findings.

In certain embodiments, the electrolyte includes LiTFSI in an amount ofat least 50 mol-%, of the total moles of electrolyte salt (or at aconcentration of at least 0.5M). In certain embodiments, the electrolyteincludes LiTFSI in an amount of up to 100 mol-% of the total moles ofelectrolyte salt (or at a concentration of up to 5.5M).

In certain embodiments, if LiPF₆ is present in the electrolyte, it ispresent in an amount of no greater than 25 mol-% of the total moles ofelectrolyte salt (or at a concentration of up to 0.3M). In certainembodiments, the electrolyte includes LiPF₆ at a concentration of atleast 0.01M (or in an amount of at least 1 mole-% of the total moles ofelectrolyte salt).

In certain embodiments, the electrolyte includes LiBOB in an amount ofat least 2 mol-% of the total moles of electrolyte salt (or at aconcentration of at least 0.01M). In certain embodiments, theelectrolyte includes LiBOB up to the solubility limit of LiBOB.

In certain embodiments, the electrolyte comprises 81.8 mol-% LiTFSI and18.2 mol-% LiBOB of the total moles of electrolyte salt (or 0.9M LiTFSIand 0.2M LiBOB).

In certain embodiments, the electrolyte includes 81.8 mol-% LiTFSI, 13.6mol-% LiBOB, and 4.5 mol-% LiPF₆ of the total moles of electrolyte salt(or 0.9M LiTFSI, 0.15M LiBOB, and 0.05M LiPF₆).

In certain embodiments, the organic solvent of the electrolyte includesa solvent having a boiling point below 140° C. Examples of such solventsinclude linear carbonates, as well as certain ethers (such as1,2-diethoxyethane (DME)), linear carboxylic esters (such as methylformate, methyl acetate, ethyl acetate, methyl propionate), and nitriles(such as acetonitrile).

In certain embodiments, the organic solvent includes a linear carbonate,such as ethylmethyl carbonate (EMC), dimethyl carbonate (DMC), diethylcarbonate (DEC), or a mixture of two or more thereof.

In certain embodiments, the organic solvent includes a mixture ofethylene carbonate (EC) and ethylmethyl carbonate (EMC). In certainembodiments, the organic solvent includes a mixture of ethylenecarbonate (EC) and ethylmethyl carbonate (EMC) in a range of 10:90 to50:50. In certain embodiments, the organic solvent includes a mixture ofethylene carbonate (EC) and ethylmethyl carbonate (EMC) in a ratio of30:70.

Significantly, because of the use of at least one linear carbonatesolvent, which has a low boiling point (bp less than or equal toexposure temperature (approximately 140° C.)) and low viscosity (highionic conductivity), and the use of a lithium salt or combination ofsalts to stabilize such low boiling solvent (up to the exposuretemperature), while maintaining a high electrolyte conductivity forapplication temperature, the lithium ion batteries of the presentdisclosure are simultaneously capable of surviving exposure to anelevated temperature as high as 140° C. for up to 3 hours (temperaturesand times experienced, for example, during steam sterilization), whilemaintaining a high delivered power when subsequently used at applicationtemperature. In certain embodiments, as a result of the combination ofthe low boiling point solvent(s) and the selected lithium salt(s), thelithium ion batteries of the present disclosure withstand a standardsteam autoclave cycle (134° C. for 18 minutes) and maintain usability atapplication temperature for 100 to 300 cycles.

In certain embodiments, the organic solvent further includes a cycliccarbonate, such as ethylene carbonate (EC), propylene carbonate (PC),butylene carbonate (BC), fluoroethylene carbonate (FEC), or a mixture oftwo or more thereof. If used, these high boiling point (bp) solvents (bpgreater than or equal to 140° C.) are used in a small amount because atapplication temperature, they have very high viscosities (and thereforelow ionic conductivities), resulting in poor application temperaturepower performance (see, e.g., Kang Xu, Chemical Reviews, 104, 4303-4417(2004)). Thus, if used, they are used in an amount of up to 50 wt-%, orup to 40 wt-%, or up to 30 wt-%.

The amount of organic solvent used in the electrolyte is dependent onbattery size, and other parameters that are application driven.

In certain embodiments, the electrolyte includes a polymer, therebyforming a gel. In certain embodiments, such polymers include PEO(poly(ethylene oxide)), PEGDA (poly(ethylene glycol diacrylate)), PVDF(poly(vinylidene fluoride)), PVDF-HFP (poly(vinylidenefluoride-co-hexafluorophosphate)), PMMA (poly(methyl methacrylate)),methyl cellulose, hypromellose, poly(butyl acrylate) and similaracrylates.

In certain embodiments, the electrolyte includes an electrolyteadditive. Such electrolyte additives are typically used to enable highervoltage operation (e.g., greater than 4.2V), but are used herein atlower voltages (e.g., 4.1V) and at high temperatures (e.g., 140° C.).

In certain embodiments, the electrolyte additive is selected from anunsaturated compound (such as vinylene carbonate (VC) and vinyl ethylenecarbonate (VEC)), a sulfur-containing compound (such as 1,3-propanesultone (PS), prop-1-ene 1,3-sultone (PES),1,3,2-dioxathiolane-2,2-dioxide (DTD), trimethylene sulfate (TMS), andmethylene methyl disulfonate (MMDS)), a boron-containing compound (suchas trimethylboroxine and trimethoxyboroxine (TMOBX)), aphosphorus-containing compound (such astris(1,1,1,3,3,3-hexafluoro-2-isopropyl)phosphate (HFiP),tris(trimethylsilyl) phosphate (TTSP), tris(trimethylsilyl) phosphite(TTSPi), and triallyl phosphate (TAP)), an aromatic compound (such asbiphenyl (BP)), a heterocyclic compound (such as thiophene (TP)), aLewis acid-base adduct (such as pyridine-boron trifluoride (PBF)), and amixture of two or more thereof.

In certain embodiments, the boron-containing additives includeboroxine-containing compounds (e.g., trimethylboroxine andtrimethoxyboroxine (TMOBX) or its derivatives), compounds includingboroxine rings with polyalkylene oxide chains (e.g.,tris(poly(oxyethylene)) boroxine), and compounds having boroxine ringswith substituted or unsubstituted phenyl rings (e.g., triphenylboroxine, tris(4-fluorophenyl) boroxine, and tris(pentafluorophenyl)boroxine). Other boron-containing compounds include derivatives ofboronate esters and borinate esters such as difluorophenoxy methylborane, dihexafluoroisopropoxy methyl borane, dihexafluoroisopropoxyphenyl borane.

In certain embodiments, the electrolyte additive is present in theelectrolyte in an amount of at least 5 wt-%. In certain embodiments, theelectrolyte additive is present in the electrolyte in an amount of up to10 wt-%. The amount of electrolyte additive, however, depends on batterysize, and other parameters that are application driven.

Battery Encasement and Methods of Making Batteries

A typical battery includes one or more cells that include a negativeelectrode, a positive electrode, a separator between the negative andpositive electrodes, and an electrolyte encased in an encasementtypically made of a corrosion-resistant material. Thecorrosion-resistant material may be, for example, aluminum, stainlesssteel, aluminum laminate, ceramic, or combinations thereof.

In certain embodiments, the encasement is hermetically sealed. Suchhermetic seal prevents transfer of gas and/or liquid in or out of theencasement. Suitable hermetically sealed encasements include glass orceramic insulator around a feed through, as described, for example, inU.S. Pat. No. 5,104,755 (Taylor et al.) and U.S. Pat. No. 4,678,868(Kraska et al.).

Lithium ion batteries of the present disclosure can be constructed usingwell known techniques, such as those described in the Examples Section.

Methods of Sterilizing Batteries

The present disclosure includes methods for sterilizing lithium ionbatteries. In certain embodiments, such methods include the lithium ionbatteries disclosed herein, although other lithium ion batteries may besterilized using the present method.

In certain embodiments, a method for sterilizing a lithium ion batteryincludes: providing a lithium ion battery; either charging ordischarging the battery to a state of charge (SOC) of 20% to 100%; andsteam sterilizing the battery to form a sterilized lithium ion battery.

In certain embodiments, the method includes either charging ordischarging the battery to a state of charge (SOC) of 20% to 100%, or20% to 80%, or 40% to 60%. In certain embodiments, the method includeseither charging or discharging the battery to a state of charge (SOC) of50%. A 50% SOC is where the positive and negative electrode materialsare most stable. At too high SOC, oxidation of electrolyte at thepositive electrode can occur. At too low SOC, reduction of componentscan occur.

The steam sterilizing step is typically carried out at a controlledtemperature, which may vary with sterilizer (e.g., autoclave). Therecommendation from the U.S. Center for Disease Control on steamsterilization includes minimum exposure periods (for sterilization ofwrapped healthcare supplies) of 30 minutes at 121° C. (250° F.) in agravity displacement sterilizer or 4 minutes at 132° C. (270° C.) in aprevacuum sterilizer (see, e.g.,https://www.cdc.gov/hicpac/Disinfection_Sterilization/13_0Sterilization.html).The recommendation from the French Ministry of Health is moreextreme—steam autoclave cycle of 134° C. for 18 minutes (see, forexample, French Ministry of Health: DGS/5 C/DHOS/E 2 no 2001-138 (14Mar. 2001) athttp://social-sante.gouv.fr/fichiers/bo/2001/01-1/a0110756.htm.

In certain embodiments, a battery of the present disclosure can survive(e.g., as in steam sterilization) a temperature of at least 100° C., orat least 121° C., or at least 132° C., or at least 135° C., or at least140° C. In certain embodiments, a battery of the present disclosure canwithstand such high temperatures (e.g., as in steam sterilization) forat least 4 minutes, or at least 12 minutes, or at least 18 minutes, orat least 90 minutes, or at least 120 minutes, or at least 180 minutes,or at least 360 minutes.

In certain embodiments, a battery of the present disclosure can survivea temperature of up to 300° C., or up to 250° C., for up to 168 hours.Typically, however, steam sterilizing a battery occurs at a temperatureof no greater than 134° C. for a time of no greater than 18 minutes atthe maximum temperature.

In certain embodiments, a battery of the present disclosure can survive(e.g., as in steam sterilization) a temperature of at least 100° C. fora time of at least 4 minutes, or at least 12 minutes, or at least 18minutes, or at least 90 minutes, or at least 120 minutes, or at least180 minutes, or at least 360 minutes.

In certain embodiments, a battery of the present disclosure can survive(e.g., as in steam sterilization) a temperature of at least 121° C. fora time of at least 4 minutes, or at least 12 minutes, or at least 18minutes, or at least 90 minutes, or at least 120 minutes, or at least180 minutes, or at least 360 minutes.

In certain embodiments, a battery of the present disclosure can survive(e.g., as in steam sterilization) a temperature of at least 132° C. fora time of at least 4 minutes, or at least 12 minutes, or at least 18minutes, or at least 90 minutes, or at least 120 minutes, or at least180 minutes, or at least 360 minutes.

In certain embodiments, a battery of the present disclosure can survive(e.g., as in steam sterilization) a temperature of at least 135° C. fora time of at least 4 minutes, or at least 12 minutes, or at least 18minutes, or at least 90 minutes, or at least 120 minutes, or at least180 minutes, or at least 360 minutes.

In certain embodiments, a battery of the present disclosure can survive(e.g., as in steam sterilization) a temperature of at least 140° C. fora time of at least 4 minutes, or at least 12 minutes, or at least 18minutes, or at least 90 minutes, or at least 120 minutes, or at least180 minutes, or at least 360 minutes.

In certain embodiments, after using the various conditions (e.g.,sterilization conditions) described, the battery retains a capacity ofat least 80% of the capacity at application temperature of a batteryhaving the same construction that has not been sterilized. In certainembodiments, the method further includes charging the sterilized lithiumion battery to 100% while maintaining sterilization.

In certain embodiments, the method includes the steps of either chargingor discharging the battery and steam sterilizing at least 2 times, or atleast 10 times. In certain embodiments, the method includes the steps ofeither charging or discharging the battery and steam sterilizing up to500 times.

Exemplary Embodiments of the Disclosure

Embodiment 1 is a lithium ion battery comprising:

a positive electrode comprising:

a positive current collector comprising aluminum;

positive electrode material comprising a lithium-containing metal oxideor a lithium-containing metal phosphate;

a binder; and

conductive carbon:

a negative electrode comprising:

a negative current collector comprising copper, aluminum, titanium, orcarbon;

negative electrode material comprising a lithium titanium oxide, acarbon-containing material capable of intercalating lithium, ametal-alloy containing material capable of intercalating lithium, or acombination thereof;

a binder; and

conductive carbon:

a separator comprising a material having a melt temperature of greaterthan 150° C.; and

an electrolyte comprising an organic solvent and a lithium salt;

wherein the organic solvent comprises a solvent having a boiling pointbelow 140° C. (e.g., a linear carbonate):

wherein the lithium salt comprises lithiumbis(trifluoromethanesulfonimide) (LiTFSI); and

wherein, after exposure to conditions comprising a temperature of atleast 100° C. for a time of at least 4 minutes, the battery retains acapacity of at least 80% of the capacity at application temperature of abattery having the same construction that has not been subjected to suchconditions.

Embodiment 2 is the battery of embodiment 1 wherein the positive currentcollector comprises surface-treated aluminum.

Embodiment 3 is the battery of embodiment 2 wherein the surface-treatedaluminum comprises carbon-coated aluminum.

Embodiment 4 is the battery of any one of embodiments 1 through 3wherein the positive electrode material comprises a lithium-containingmetal oxide, which is optionally surface treated.

Embodiment 5 is the battery of embodiment 4 wherein the surface-treatedpositive electrode material comprises a surface treatment selected froma metal oxide (Al₂O₃, etc.), a metal phosphate (LaPO₄, etc.), a metalhalide, carbon, or a mixture thereof.

Embodiment 6 is the battery of embodiment 5 wherein thelithium-containing metal oxide comprises LiCoO₂ or LiNiCoMn/AlO₂.

Embodiment 7 is the battery of any one of embodiments 1 through 6wherein the positive electrode material comprises a lithium-containingmetal phosphate.

Embodiment 8 is the battery of embodiment 7 wherein thelithium-containing metal phosphate comprises LiFePO₄.

Embodiment 9 is the battery of any one of embodiments 1 through 8wherein the positive electrode binder comprises carboxy methyl cellulose(CMC), styrene-butadiene rubber (SBR), polyvinylidene fluoride (PVDF),polytetrafluoroethylene (PTFE), or a mixture of two or more thereof.

Embodiment 10 is the battery of embodiment 9 wherein the positiveelectrode binder comprises PVDF.

Embodiment 11 is the battery of embodiment 9 or 10 wherein the positiveelectrode comprises a binder in an amount of at least 0.1 wt-%, based onthe total weight of the dry cathode mix (without solvent).

Embodiment 12 is the battery of any one of embodiments 9 through 11wherein the positive electrode comprises a binder in an amount of up to10 wt-%, based on the total weight of the dry cathode mix (withoutsolvent).

Embodiment 13 is the battery of any one of embodiments 1 through 12wherein the negative current collector is surface treated.

Embodiment 14 is the battery of embodiment 13 wherein thesurface-treated negative current collector comprises a surface treatmentselected from a carbon coating, a nitrogen coating, or an oxide coatingon copper, aluminum, titanium, or carbon.

Embodiment 15 is the battery of any one of embodiments 1 through 14wherein the negative current collector comprises copper (particularlywhen the negative electrode material comprises graphite).

Embodiment 16 is the battery of any one of embodiments 1 through 14wherein the negative current collector comprises aluminum (particularlywhen the negative electrode material comprises a lithium titaniumoxide).

Embodiment 17 is the battery of any one of embodiments 1 through 16wherein the negative electrode material comprises a lithium titaniumoxide.

Embodiment 18 is the battery of embodiment 17 wherein the lithiumtitanium oxide is a lithium titanate spinel selected from the group of:Li₄M_(x)Ti_(15−x)O₁₂ (wherein M is metal selected from aluminum,magnesium, nickel, cobalt, iron, manganese, vanadium, copper, chromium,molybdenum, niobium, or combinations thereof and x=0-1); Li_(x)Ti_(y)O₄(wherein x=0-4, and y=0-2); Li₂TiO₃; Li₄Ti₅O₁₂; Li₄Ti_(4.75)V_(0.25)O₁₂;Li₄Ti_(4.75)Fe_(0.25)O_(11.88); Li₄Ti_(4.5)Mn_(0.5)O₁₂; and LiM′M″XO₄(wherein: M′ is a metal selected from nickel, cobalt, iron, manganese,vanadium, copper, chromium, molybdenum, niobium, or combinationsthereof; M″ is a three valent non-transition metal, and X is zirconium,titanium, or a combination of these two).

Embodiment 19 is the battery of embodiment 18 wherein the lithiumtitanium oxide is of the formula Li₄Ti₅O₁₂ (sometimes referred to asLi_(1+x)[Li_(1/3)Ti_(5/3)]O₄, with 0≤x<1).

Embodiment 20 is the battery of any one of embodiments 1 through 16wherein the negative electrode material comprises a carbon-containingmaterial capable of intercalating lithium.

Embodiment 21 is the battery of embodiment 20 wherein the negativeelectrode material comprises graphite.

Embodiment 22 is the battery of embodiment 21 wherein the graphitecomprises artificial graphite (e.g., MCMB).

Embodiment 23 is the battery of any one of embodiments 1 through 22wherein the negative electrode binder comprises carboxy methyl cellulose(CMC), styrene-butadiene rubber (SBR), polyvinylidene fluoride (PVDF),polytetrafluoroethylene (PTFE), or a mixture of two or more thereof.

Embodiment 24 is the battery of embodiment 23 wherein the negativeelectrode binder comprises PVDF.

Embodiment 25 is the battery of any one of embodiments 1 through 24wherein the negative electrode comprises a binder in an amount of atleast 1 wt-%, based on the total weight of the dry anode mix (withoutsolvent).

Embodiment 26 is the battery of any one of embodiments 1 through 25wherein the negative electrode comprises a binder in an amount of up to10 wt-%, based on the total weight of the dry anode mix (withoutsolvent).

Embodiment 27 is the battery of any one of embodiments 1 through 26wherein the separator comprises one or more layers of material having amelt temperature of greater than 150° C. In certain embodiments, theseparator includes multiple separator layers with different meltingpoints, which may be laminated together to form a single multi-layercomposite separator.

Embodiment 28 is the battery of any one of embodiments 1 through 27wherein separator comprises a polyimide, polyolefin (such aspolypropylene), polyethylene terephthalate, ceramic-coated polyolefin,cellulose, or a mixture of two or more thereof.

Embodiment 29 is the battery of embodiment 27 or 28 wherein theseparator comprises a combination of microfibers and nanofibers.

Embodiment 30 is the battery of embodiment 29 wherein the separatorcomprises polyethylene terephthalate microfibers and cellulosenanofibers.

Embodiment 31 is the battery of any one of embodiments 1 through 30wherein the separator is no more than 250 microns thick.

Embodiment 32 is the battery of any one of embodiments 1 through 31wherein the electrolyte comprises LiTFSI in an amount of at least 50mol-% of the total moles of electrolyte salt (or at a concentration ofat least 0.5M).

Embodiment 33 is the battery of any one of embodiments 1 through 32wherein the electrolyte comprises LiTFSI in an amount of up to 100 mol-%of the total moles of electrolyte salt (or at a concentration of up to5.5M).

Embodiment 34 is the battery of any one of embodiments 1 through 33wherein the electrolyte comprises a combination of lithium salts.

Embodiment 35 is the battery of any one of embodiments 1 through 33wherein the electrolyte salt consists of one or more lithium salts.

Embodiment 36 is the battery of any one of embodiments 1 through 35wherein the electrolyte salt further comprises a lithium salt selectedfrom lithium bis(oxalato)borate (LiBOB), lithiumbis(pentafluoroethylsulfonyl)imide (LiBETI), lithiumbis(fluorosulfonyl)imide (LiFSI), lithium difluoro(oxalato)borate(LiDFOB), lithium tetrafluoroborate (LiBF₄), lithiumtrifluoromethanesulfonate (LiTriflate), lithium hexafluoroarsenate(LiAsF₆), lithium hexafluorophosphate (LiPF₆), or a mixture of two ormore thereof.

Embodiment 37 is the battery of embodiment 36 wherein the electrolytesalt comprises LiTFSI and LiBOB.

Embodiment 38 is the battery of embodiment 36 or 37 wherein theelectrolyte salt comprises LiTFSI, LiPF₆, and LiBOB.

Embodiment 39 is the battery of embodiment 38 wherein LiPF₆ is presentin an amount of no greater than 25 mol-% of the total moles ofelectrolyte salt (or at a concentration of up to 0.3M).

Embodiment 40 is the battery of embodiment 38 or 39 wherein theelectrolyte comprises LiPF₆ in an amount of at least 1 mol-% of thetotal moles of electrolyte salt (or at a concentration of at least0.01M).

Embodiment 41 is the battery of any one of embodiments 37 through 40wherein the electrolyte comprises LiBOB in an amount of at least 2 mol-%of the total moles of electrolyte salt (or at a concentration of atleast 0.01M).

Embodiment 42 is the battery of any one of embodiments 37 through 41wherein the electrolyte comprises LiBOB at a concentration up to thesolubility limit of LiBOB.

Embodiment 43 is the battery embodiment 37 wherein the electrolytecomprises 81.8 mol-% LiTFSI and 18.2 mol-% LiBOB of the total moles ofelectrolyte salt (or 0.9M LiTFSI and 0.2M LiBOB).

Embodiment 44 is the battery of embodiment 38 wherein the electrolytecomprises 81.8 mol-% LiTFSI, 13.6 mol-% LiBOB, and 4.5 mol-% LiPF₆ ofthe total moles of electrolyte salt (or 0.9M LiTFSI, 0.15M LiBOB, and0.05M LiPF₆).

Embodiment 45 is the battery of any one of embodiments 1 through 44wherein the negative electrode material comprises a metal-alloycontaining material capable of intercalating lithium.

Embodiment 46 is the battery of embodiment 45 wherein metal-alloycontaining material comprises silicon-containing material ortin-containing material that is capable of intercalating lithium.

Embodiment 47 is the battery of any one of embodiments 1 through 46wherein the organic solvent comprises a linear carbonate selected fromethylmethyl carbonate (EMC), dimethyl carbonate (DMC), diethyl carbonate(DEC), and a mixture of two or more thereof.

Embodiment 48 is the battery of embodiment 47 wherein the organicsolvent comprises a mixture of ethylene carbonate (EC) and ethylmethylcarbonate (EMC).

Embodiment 49 is the battery of embodiment 48 wherein the organicsolvent comprises a mixture of ethylene carbonate (EC) and ethylmethylcarbonate (EMC) in a range of 10:90 to 50:50.

Embodiment 50 is the battery of embodiment 49 wherein the organicsolvent comprises a mixture of ethylene carbonate (EC) and ethylmethylcarbonate (EMC) in a ratio of 30:70.

Embodiment 51 wherein the battery of any one of embodiments 1 through 50wherein the organic solvent further comprises a cyclic carbonate, or amixture of two or more thereof.

Embodiment 52 wherein the battery of embodiment 51 wherein the cycliccarbonate is selected from ethylene carbonate (EC), propylene carbonate(PC), butylene carbonate (BC), fluoroethylene carbonate (FEC), and amixture of two or more thereof.

Embodiment 53 is the battery of any of embodiments 1 through 52 whereinthe electrolyte comprises a polymer, forming a gel electrolyte.

Embodiment 54 is the battery of embodiment 53 wherein the polymer isselected from PEO (poly(ethylene oxide)), PEGDA (poly(ethylene glycoldiacrylate)), PVDF (poly(vinylidene fluoride)), PVDF-HFP(poly(vinylidene floride-co-hexafluorophosphate)), PMMA (poly(methylmethacrylate)), methyl cellulose, hypromellose, poly(butyl acrylate) andsimilar acrylates.

Embodiment 55 is the battery of any one of embodiments 1 through 54wherein the electrolyte comprising an electrolyte additive.

Embodiment 56 is the battery of embodiment 55 wherein the electrolyteadditive is selected from an unsaturated compound (such as vinylenecarbonate (VC) and vinyl ethylene carbonate (VEC)), a sulfur-containingcompound (such as 1,3-propane sultone (PS), prop-1-ene 1,3-sultone(PES), 1,3,2-dioxathiolane-2,2-dioxide (DTD), trimethylene sulfate(TMS), and methylene methyl disulfonate (MMDS)), a boron-containingcompound (such as trimethylboroxin and trimethoxyboroxine (TMOBX)), aphosphorus-containing compound (such astris(1,1,1,3,3,3-hexafluoro-2-isopropyl)phosphate (HFiP),tris(trimethylsilyl) phosphate (TTSP), tris(trimethylsilyl) phosphite(TTSPi), and triallyl phosphate (TAP)), an aromatic compound (such asbiphenyl (BP)), a heterocyclic compound (such as thiophene (TP)), aLewis acid-base adduct (such as pyridine-boron trifluoride (PBF)), and amixture of two or more thereof.

Embodiment 57 is the battery of embodiment 55 or 56 wherein theelectrolyte additive is present in the electrolyte in an amount of 5wt-% to 10 wt-%.

Embodiment 58 is the battery of any one of embodiments 1 through 57further comprising an encasement.

Embodiment 59 is the battery of embodiment 58 wherein the encasement ismade of a corrosion-resistant material.

Embodiment 60 is the battery of embodiment 59 wherein thecorrosion-resistant material comprises aluminum, stainless steel,aluminum laminate, ceramic, or combinations thereof.

Embodiment 61 is the battery of any one of embodiments 58 through 60wherein the encasement is hermetically sealed.

Embodiment 62 is the battery of embodiment 61 wherein the hermeticallysealed encasement comprises glass or ceramic insulator around a feedthrough.

Embodiment 63 is a lithium ion battery comprising:

a positive electrode comprising:

a positive current collector comprising carbon-coated aluminum;

positive electrode material comprising LiCoO₂:

a binder; and

conductive carbon;

a negative electrode comprising:

a negative current collector comprising copper;

negative electrode material comprising artificial graphite;

a binder; and

conductive carbon;

a separator comprising a material having a melt temperature of greaterthan 150° C.:

an electrolyte comprising:

a lithium salt comprising a combination of LiTFSI. LiBOB, and LiPF₆; and

an organic solvent comprising a mixture of ethylene carbonate (EC) andethylmethyl carbonate (EMC); and

a hermetically sealed encasement;

wherein, after exposure to conditions comprising a temperature of atleast 100° C. for a time of at least 4 minutes, the battery retains acapacity of at least 80% of the capacity at application temperature of abattery having the same construction that has not been subjected to suchconditions.

Embodiment 64 is the battery of embodiment 63 wherein the electrolytecomprises LiTFSI in an amount of 50 mol-% to 100 mol-% of the totalmoles of electrolyte salt (or at a concentration of 0.5M to 5.5M).

Embodiment 65 is the battery of embodiment 63 or 64 wherein theelectrolyte comprises LiBOB in an amount of at least 2 mol-% of thetotal moles of electrolyte salt (or at a concentration of 0.01M), up tothe solubility limit of LiBOB.

Embodiment 66 is the battery of any one of embodiments 63 through 65wherein LiPF₆ is present in an amount of no greater than 25 mol-% of thetotal moles of electrolyte salt (or at a concentration of up to 0.3M).

Embodiment 67 is the battery of embodiment 66 wherein the electrolytecomprises LiPF₆ at a concentration of at least 0.01M (or in an amount ofat least 1 mole-% of the total moles of electrolyte salt).

Embodiment 68 is the battery of any one of embodiments 63 through 67wherein, after exposure to conditions comprising a temperature of atleast 100° C. for a time of at least 4 minutes, or at least 12 minutes,or at least 18 minutes, or at least 90 minutes, or at least 120 minutes,or at least 180 minutes, or at least 360 minutes, the battery retains acapacity of at least 80% of the capacity at application temperature of abattery having the same construction that has not been subjected to suchconditions.

Embodiment 69 is the battery of any one of the preceding embodimentswherein, after exposure to conditions comprising a temperature of atleast 121° C. for a time of at least 4 minutes, or at least 12 minutes,or at least 18 minutes, or at least 90 minutes, or at least 120 minutes,or at least 180 minutes, or at least 360 minutes, the battery retains acapacity of at least 80% of the capacity at application temperature of abattery having the same construction that has not been subjected to suchconditions.

Embodiment 70 is the battery of any one of the preceding embodimentswherein, after exposure to conditions comprising a temperature of atleast 132° C. for a time of at least 4 minutes, or at least 12 minutes,or at least 18 minutes, or at least 90 minutes, or at least 120 minutes,or at least 180 minutes, or at least 360 minutes, the battery retains acapacity of at least 80% of the capacity at application temperature of abattery having the same construction that has not been subjected to suchconditions.

Embodiment 71 is the battery of any one of the preceding embodimentswherein, after exposure to conditions comprising a temperature of atleast 135° C. for a time of at least 4 minutes, or at least 12 minutes,or at least 18 minutes, or at least 90 minutes, or at least 120 minutes,or at least 180 minutes, or at least 360 minutes, the battery retains acapacity of at least 80% of the capacity at application temperature of abattery having the same construction that has not been subjected to suchconditions.

Embodiment 72 is the battery of any one of the preceding embodimentswherein, after exposure to conditions comprising a temperature of atleast 140° C. for a time of at least 4 minutes, or at least 12 minutes,or at least 18 minutes, or at least 90 minutes, or at least 120 minutes,or at least 180 minutes, or at least 360 minutes, the battery retains acapacity of at least 80% of the capacity at application temperature of abattery having the same construction that has not been subjected to suchconditions.

Embodiment 73 is a method for sterilizing a lithium ion battery, themethod comprising: providing a lithium ion battery; either charging ordischarging the battery to a state of charge (SOC) of 20% to 100%; andsteam sterilizing the battery to form a sterilized lithium ion battery.

Embodiment 74 is the method of embodiment 73 wherein providing a lithiumion battery comprises providing a lithium ion battery of any one ofembodiments 1 through 72.

Embodiment 75 is the method of embodiment 73 or 74 comprising eithercharging or discharging the battery to a state of charge (SOC) of 20% to80%.

Embodiment 76 is the method of embodiment 75 comprising either chargingor discharging the battery to a state of charge (SOC) of 40% to 60%.

Embodiment 77 is the method of embodiment 76 comprising either chargingor discharging the battery to a state of charge (SOC) of 50%.

Embodiment 78 is the method of any one of embodiments 73 through 77wherein steam sterilizing the battery includes subjecting the battery toa temperature of at least 100° C., or at least 121° C., or at least 132°C., or at least 135° C., or at least 140° C.

Embodiment 79 is the method of any one of embodiments 73 through 78wherein steam sterilizing the battery includes subjecting the battery tosteam sterilization for at least 4 minutes, or at least 12 minutes, orat least 18 minutes, or at least 90 minutes, or at least 120 minutes, orat least 180 minutes, or at least 360 minutes.

Embodiment 80 is the method of any one of embodiments 73 through 79wherein steam sterilizing the battery occurs at a temperature of atleast 100° C. for a time of at least 4 minutes, or at least 12 minutes,or at least 18 minutes, or at least 90 minutes, or at least 120 minutes,or at least 180 minutes, or at least 360 minutes.

Embodiment 81 is the method of any one of embodiments 73 through 80wherein steam sterilizing the battery occurs at a temperature of atleast 121° C. for a time of at least 4 minutes, or at least 12 minutes,or at least 18 minutes, or at least 90 minutes, or at least 120 minutes,or at least 180 minutes, or at least 360 minutes.

Embodiment 82 is the method of any one of embodiments 73 through 81wherein steam sterilizing the battery occurs at a temperature of atleast 132° C. for a time of at least 4 minutes, or at least 12 minutes,or at least 18 minutes, or at least 90 minutes, or at least 120 minutes,or at least 180 minutes, or at least 360 minutes.

Embodiment 83 is the method of any one of embodiments 73 through 82wherein steam sterilizing the battery occurs at a temperature of atleast 135° C. for a time of at least 4 minutes, or at least 12 minutes,or at least 18 minutes, or at least 90 minutes, or at least 120 minutes,or at least 180 minutes, or at least 360 minutes.

Embodiment 84 is the method of any one of embodiments 73 through 83wherein steam sterilizing the battery occurs at a temperature of atleast 140° C. for a time of at least 4 minutes, or at least 12 minutes,or at least 18 minutes, or at least 90 minutes, or at least 120 minutes,or at least 180 minutes, or at least 360 minutes.

Embodiment 85 is the method of any of embodiments 73 through 84 whereinthe battery retains a capacity of at least 80% of the capacity atapplication temperature of a battery having the same construction thathas not been sterilized.

Embodiment 86 is the method of any one of embodiments 73 through 85further comprising charging the sterilized lithium ion battery to 100%while maintaining sterilization.

Embodiment 87 is the method of any one of embodiments 73 through 86comprising either charging or discharging the battery and steamsterilizing at least 2 times.

Embodiment 88 is the method of embodiment 87 comprising either chargingor discharging the battery and steam sterilizing at least 10 times.

Embodiment 89 is the method of embodiment 87 or 88 comprising eithercharging or discharging the battery and steam sterilizing up to 500times.

EXAMPLES

Objects and advantages of this disclosure are further illustrated by thefollowing examples, but the particular materials and amounts thereofrecited in these examples, as well as other conditions and details,should not be construed to unduly limit this disclosure.

Cell Construction

Lithium ion cells of 100 mAh nominal capacity were constructed asspirally wound prismatic cells in a stainless-steel enclosure that washermetically scaled and used a glass feedthrough. The positiveelectrodes were comprised of LiCoO₂ positive active material coated ontoa carbon-coated aluminum current collector. The negative electrodes werecomprised of artificial graphite negative active material coated onto acopper current collector. The positive and negative electrodes wereprepared using a slurry coating and calendering process. Both electrodesincluded their respective active materials described above, a conductivecarbon diluent, and a polymeric PVDF binder. The cells were filled with1.5±0.1 g of electrolyte, the composition of which is described inTable 1. For Examples 1, 2, 3, and 5 the separator was a 25 μm nanofibermembrane with a melt integrity of 300° C., sold under the tradename ofSILVER from Dreamweaver International (Greer, S.C.); while for Example 4the separator was a 25 μm TWARON aramid nanofiber membrane with a meltintegrity of 300° C. (available from Teijin Aramid), sold under thetradename of GOLD from Dreamweaver International (Greer, S.C.). Examples2A and 2B had the same electrolyte composition, but varied in theseparator material; for Example 2A the separator was Dreamweaver GOLDand Example 2B the separator was a 20 μm polyimide membrane with a meltintegrity of approximately 450° C.

TABLE 1 Summary of cell construction differences for 5 examplesdescribed. Exam- ple Salt(s) Solvent Mixture Separator 1 1.2M LiPF₆ 3:7w:w EC:EMC DW SILVER 2 0.9M LiTFSI + 0.2M 3:7 w:w EC:EMC DW SILVER LiBOB2A 0.9M LiTFSI + 0.2M 3:7 w:w EC:EMC DW GOLD LiBOB 2B 0.9M LiTFSI + 0.2M3:7 w:w EC:EMC Polyimide LiBOB 3 1.05M LiTFSI + 0.05M 3:7 w:w EC:EMC DWSILVER LiPF₆ 4 0.9M LiTFSI + 0.15M 3:7 w:w EC:EMC DW GOLD LiBOB + 0.05MLiPF₆ 5 0.9M LiTFSI + 0.2M 1:1 w:w EC:PC DW SILVER LiBOB DW =Dreamweaver

Experimental Protocol

Within 24 hours of filling the cells with electrolyte and sealing thecells, the cells were put through a formation protocol, described by:

1. Constant current (CC) charge at a rate of 0.1 C (current of 10 mA) toan upper cutoff voltage of 4.1 V

2. Constant voltage (CV) hold at 4.1 V for 4 hours

3. Open circuit storage for 30 hours

4. CC discharge at a rate of 0.1 C (current of 10 mA) to a lower cutoffvoltage of 3.575 V

5. Open circuit storage for 10 minutes

6. CC charge at a rate of 0.1 C (current of 10 mA) to an upper cutoffvoltage of 4.1 V

7. CV hold at 4.1 V for 1 hour

8. Open circuit storage for a minimum of 1 hour

Once the formation protocol was complete, all cells proceeded through aninitial electrochemical performance test, described by:

1. 12 CC-CV charge—CC discharge cycles of 0.5 C (50 mA) CC charge to 4.1V with a CV hold at 4.1 V until the current was less than or equal to4.2 mA, and 0.5 C (50 mA) CC discharge to 3.575 V

2. 1 CC-CV charge—CC discharge cycle of 0.1 C (10 mA) CC charge to 4.1 Vwith a CV hold at 4.1 V until the current was less than or equal to 4.2mA, and 0.1 C (10 mA) CC discharge to 3.575 V

3. CC-CV charge at a rate of 0.1 C (10 mA) to 3.8 V with a CV hold at4.1 V until the current was less than or equal to 4.2 mA

Following the initial electrochemical performance test described above,the 1 kHz AC impedance and center thickness were measured at 20° C. forall cells and then the cells were divided into two groups: one controlgroup and one exposed group. The control group remained at roomtemperature while the exposed group cells were placed into a convectionoven at a temperature of 135° C. for two hours. Following the 135° C.exposure, the cells were allowed to cool to room temperature, then boththe control and exposed group cells proceeded through a finalelectrochemical performance test, described by:

1. 14 CC-CV charge—CC discharge cycles of 0.5 C (50 mA) CC charge to 4.1V with a CV hold at 4.1 V until the current was less than or equal to4.2 mA, and 0.5 C (50 mA) CC discharge to 3.575 V

2. 1 CC-CV charge—CC discharge cycle of 0.1 C (10 mA) CC charge to 4.1 Vwith a CV hold at 4.1 V until the current was less than or equal to 4.2mA, and 0.1 C (10 mA) CC discharge to 3.575 V

3. CC-CV charge at a rate of 0.1 C (10 mA) to 3.8 V with a CV hold at4.1 V until the current was less than or equal to 4.2 mA

Following the final electrochemical performance test described above,the 1 kHz AC impedance and center thickness were measured at 20° C. forall cells.

Results

FIG. 1 shows the measured discharge capacity in mAh of the finalelectrochemical performance test for the control (open symbols) andexposed groups (closed symbols) for Examples 1 through 4 as defined inTable 1. As described above, cycles 14 through 27 were performed at a0.5 C rate and cycle 28 was at a 0.1 C rate. For clarity, two regions inFIG. 1, marked (a) and (b) are expanded in FIG. 2 and FIG. 3,respectively.

FIG. 4 shows the impact of separator choice on the measured dischargecapacity for the initial electrochemical performance test for Examples2, 2A, and 2B. FIG. 5 shows the measured discharge capacity in mAh ofthe final electrochemical performance test for the control (opensymbols) and exposed (closed symbols) groups for Examples 2 and 5.Examples 2 and 5 have the same electrolyte salt composition and varyonly in the solvent composition.

Table 2 gives a summary of the average measured discharge capacities atboth 0.5 C and 0.1 C rates for both control and exposed cells for all 5examples described. The 0.5 C discharge capacities were tabulated forcycle 27 (the last of the final electrochemical performance test 0.5 Ccycles). The ratio of the discharge capacity measured at 0.5 C to thethat measured at 0.1 C is tabulated as a measure of the power capabilityof the cell; i.e., the ability to deliver a large fraction of its totalavailable capacity at a high (e.g., 0.5 C) rate. The percentage ofretained capacity as a result of exposure at both 0.5 C and 0.1 C isalso tabulated, and is defined as the ratio of the measured capacitiesof the exposed cells to the measured capacities of the control cells atthe given rate.

TABLE 2 Summary of average measured discharge capacities (Q_(d)) andcomparison of capacity of exposed cells to control cells Control ControlControl Exposed Exposed %0.5 C %0.1 C Exam- 0.5 C Q_(d) 0.1 C Q_(d) (0.5C Q_(d)/ 0.5 C Q_(d) 0.1 C Q_(d) Q_(d) Q_(d) ple (mAh) (mAh) 0.1 C Q_(d)(mAh) (mAh) retained retained 1 112.4 118.1 0.95 0.0 0.0 0.0 0.0 2 93.9108.0 0.87 92.6 108.1 98.6 100.2 3 107.7 117.2 0.92 0.0 0.0 0.0 0.0 492.5 109.0 0.85 91.3 107.4 98.7 98.5 5 17.8 89.0 0.20 4.0 43.9 22.6 49.4

Table 3 gives a summary of the average percent increase of the 1 kHz ACimpedance and the cell thickness as a result of the high temperatureexposure. In both cases the increase is calculated as the differencebetween the measurements taken after the final and initialelectrochemical performance tests divided by the measurements takenafter the initial tests, and then converted to a percentage. Onlyresults for the exposed cells are tabulated.

TABLE 3 Summary of percentage increase of 1 kHz AC impedance and cellthickness as a result of 135° C. exposure for 2 hours Exam- Percent 1kHz AC Percent Cell ple Impedance Increase Thickness Increase 1 3870.677.9 2 16.4 5.8 3 452.0 54.5 4 27.4 4.9 5 33.5 24.2

Cells containing only LiPF₆ as an electrolyte salt (Example 1,triangles) showed complete capacity loss after being exposed to 135° C.temperature. There was also a nearly 4000% increase in impedance and a78% thickness increase as a result of exposure. The cell enclosure canonly withstand approximately 80-85% thickness increase before theenclosure mechanically fails. This is in contrast to the resultspresented in U.S. Pat. Pub. No. US 2006/019164 (Bonhomme et al.) where1M LiPF₆ was the preferred electrolyte salt enabling cell operation upto 150° C.

Cells containing a combination of 0.9M LiTFSI and 0.2M LiBOB as theelectrolyte salt (Example 2, circles) showed excellent agreement in themeasured capacity between the control and exposed cells at both 0.5 Cand 0.1 C rates (99% and 100% capacity retention, respectively). Thisexemplary combination showed almost no change in the applicationtemperature (37° C.) cell performance and little increase in impedanceand thickness as a result of the 135° C. exposure for two hours, whilemaintaining high power capability at the application temperature.

Cells containing a combination of 0.9M LiTFSI and 0.2M LiBOB as theelectrolyte salt with separator consisting of Dreamweaver SILVER(Example 2, circles), Dreamweaver GOLD (Example 2A, crosses), andpolyimide (Example 2B, pluses) showed varying delivered dischargecapacities for the initial electrochemical performance tests,predominately for the higher rate (0.5 C) cycles. Initial roomtemperature (20° C., as built, before formation) 1 kHz AC impedance forthe Example 2, 2A, and 2B cells were measured to be 0.33Ω, 0.57Ω, and0.31Ω, respectively. The Dreamweaver GOLD separator has an intrinsicallyhigher impedance than both Dreamweaver SILVER and the polyimidematerial. This is in good agreement with the measured dischargecapacities.

Cells containing a combination of 1.05M LiTFSI and 0.05M LiPF₆ as theelectrolyte salt (Example 3, squares) also showed complete capacity lossafter being exposed to 135° C. temperature. Even with only 0.05M LiPF₆,the cells also showed a 450% increase in impedance and 55% increase inthickness, which was very similar to the performance of the electrolytecontaining solely LiPF₆. The results of Example 3 again contrasted theresults of U.S. Pat. Pub. No. US 2006/019164 (Bonhomme et al.) where 1MLiPF₆ was the preferred electrolyte salt enabling cell operation up to150° C.

Cells containing a combination of 0.9M LiTFSI, 0.15M LiBOB, and 0.05MLiPF₆ as the electrolyte salt (Example 4, inverted triangles) showedexcellent agreement in the measured capacity between the control andexposed cells at both 0.5 C and 0.1 C rates (99% and 99% capacityretention, respectively). Surprisingly, despite the addition of 0.05MLiPF₆ to the electrolyte which resulted in complete capacity loss inExample 3, Example 4 cells performed as well as the Example 2 cells. Asdescribed previously, the Example 4 cells were built with DreamweaverGOLD separator while all Examples were built with Dreamweaver SILVER.The Dreamweaver GOLD has an intrinsically higher impedance due to thedifference in fiber composition, as seen in comparison of the measuredcapacity for Example 2 (Dreamweaver SILVER) with Example 2A (DreamweaverGOLD). Despite the higher impedance, and therefore lowered capacity, theExample 4 cells deliver nearly the same capacity as the Example 2 cells,and higher capacity than the Example 2A cells, indicating a higherelectrolyte conductivity for the Example 4 salt combination.

Cells containing a combination of 0.9M LiTFSI and 0.2M LiBOB as theelectrolyte salt with 1:1 by weight ratio of EC:PC as the electrolytesolvent system (Example 5, diamonds) show significantly lowercapacities, for both control and exposed cells, compared to the samesalt combination with 3:7 EC:EMC solvent (Example 2). The mixture of 1:1EC:PC was the preferred solvent system used in U.S. Pat. Pub. No. US2006/019164 (Bonhommet et al.) for high temperature operation. Whilethis solvent system has demonstrated value when the operatingtemperature of the lithium ion cell is very high, the results shown heredemonstrate the severe power limitations of this solvent system with allcyclic carbonates (high boiling points) at application temperature. Theapplication temperature ratio of the discharge capacity delivered at 0.5C to that at 0.1 C is 0.20, while this ratio is 0.87 for EC:EMC solvent,making the all-high boiling point solvent system impractical for cellsdesigned to operate at application temperatures. Furthermore, with theEC:PC solvent blend, the retained capacity following 135° C. exposurewas only 23% and 49% for 0.5 C and 0.1 C cycling, respectively.

The complete disclosures of the patents, patent documents, andpublications cited herein are incorporated by reference in theirentirety as if each were individually incorporated. Variousmodifications and alterations to this disclosure will become apparent tothose skilled in the art without departing from the scope and spirit ofthis disclosure. It should be understood that this disclosure is notintended to be unduly limited by the illustrative embodiments andexamples set forth herein and that such examples and embodiments arepresented by way of example only with the scope of the disclosureintended to be limited only by the claims set forth herein as follows.

The invention claimed is:
 1. A lithium ion battery comprising: apositive electrode comprising: a positive current collector comprisingaluminum; positive electrode material comprising a lithium-containingmetal oxide or a lithium-containing metal phosphate; a binder; andconductive carbon; a negative electrode comprising: a negative currentcollector comprising copper, aluminum, titanium, or carbon; negativeelectrode material comprising a lithium titanium oxide, acarbon-containing material capable of intercalating lithium, ametal-alloy containing material capable of intercalating lithium, or acombination thereof; a binder; and conductive carbon; a separatorcomprising a material having a melt temperature of greater than 150° C.;and an electrolyte comprising an organic solvent and lithium salt;wherein the organic solvent comprises a solvent having a boiling pointbelow 140° C.; and wherein the lithium salt comprises lithiumbis(trifluoromethanesulfonimide) (LiTFSI) in an amount of 50 mol-% ormore of the total moles of electrolyte salt, lithium bis(oxalato)borate(LiBOB) in an amount of 2 mol-% or more of the total moles ofelectrolyte salt, and lithium hexafluorophosphate (LiPF₆) in an amountof 1 mol-% to 25 mol-% of the total moles of electrolyte salt.
 2. Thebattery of claim 1 wherein the organic solvent comprises a linearcarbonate.
 3. The battery of claim 2 wherein the linear carbonate isselected from ethylmethyl carbonate (EMC), dimethyl carbonate (DMC),diethyl carbonate (DEC)), and a mixture of two or more thereof.
 4. Thebattery of claim 1 wherein the organic solvent further comprises acyclic carbonate, or a mixture of two or more thereof.
 5. The battery ofclaim 1 wherein the positive current collector comprises surface-treatedaluminum.
 6. The battery of claim 1 wherein the positive electrodematerial comprises a lithium-containing metal oxide, which is optionallysurface treated.
 7. The battery of claim 1 wherein the negative currentcollector is surface treated.
 8. The battery of claim 1 wherein thenegative electrode material comprises a lithium titanium oxide.
 9. Thebattery of claim 1 wherein the negative electrode material comprises acarbon-containing material capable of intercalating lithium.
 10. Thebattery of claim 9 wherein the negative electrode material comprisesgraphite.
 11. The battery of claim 1 wherein the separator comprises oneor more layers of material comprising a first layer having a melttemperature of greater than 150° C., and a second layer having a melttemperature lower than the melt temperature of the first layer.
 12. Thebattery of claim 1 wherein the electrolyte salt further comprises alithium salt selected from lithium bis(pentafluoroethylsulfonyl)imide(LiBETI), lithium bis(fluorosulfonyl)imide (LiFSI), lithiumdifluoro(oxalato)borate (LiDFOB), lithium tetrafluoroborate (LiBF₄),lithium trifluoromethanesulfonate (LiTriflate), lithiumhexafluoroarsenate (LiAsF₆), or a mixture of two or more thereof. 13.The battery of claim 1 wherein the electrolyte salt consists essentiallyof LiTFSI, LiPF₆, and LiBOB.
 14. The battery of claim 1, wherein LiTFSIis present in an amount of about 81.8 mol-%, LiBOB is present in anamount of about 13.6 mol-%, and LiPF₆ is present in an amount of about4.5 mol-%, of the total moles of electrolyte salt.
 15. The battery ofclaim 1 wherein the electrolyte comprises an electrolyte additive.
 16. Alithium ion battery comprising: a positive electrode comprising: apositive current collector comprising carbon-coated aluminum; positiveelectrode material comprising LiCoO₂; a binder; and conductive carbon; anegative electrode comprising: a negative current collector comprisingcopper; negative electrode material comprising artificial graphite; abinder; and conductive carbon; a separator comprising a material havinga melt temperature of greater than 150° C.; an electrolyte comprising: alithium salt comprising a combination of LiTFSI, LiBOB, and LiPF₆,wherein the LiTFSI is present in an amount of 50 mol-% or more of thetotal moles of electrolyte salt, LiBOB is present in an amount of 2mol-% or more of the total moles of electrolyte salt, and the LiPF₆ ispresent in an amount of no greater than 25 mol-% of the total moles ofelectrolyte salt or at a concentration of up to 0.3M; and an organicsolvent comprising a mixture of ethylene carbonate (EC) and ethylmethylcarbonate (EMC); and a hermetically sealed encasement.
 17. The batteryof claim 1, wherein LiTFSI is present in an amount of about 0.9 M, LiBOBis present in an amount of about 0.15 M, and LiPF₆ is present in anamount of about 0.05 M.